1. Field of the Invention
This invention relates to the reconstitution of a picture image from picture point intensities in a received, data-compacted picture image and particularly to an apparatus and method of picture-reconstitution by selectively shading in the received data-compacted image with suitable intensities computed by double linear interpolations from the received picture point intensities.
2. Description of the Prior Art
Communications systems for transmitting and reproducing remotely-viewed images and other two-dimensional patterns, such as television and facsimile systems, often employ broad band transmission channels to ensure faithful reproduction at the receiver end of the remotely viewed images being transmitted. Many of these systems employ a channel capacity greater than that required to send an amount of information actually necessary to describe the remotely viewed image. As a result, various systems have been proposed to reduce the bandwidth used for the transmission of signals by reducing the amount of information necessary to define a picture image. However, many of these proposed systems do not include means in the receiver for deriving any meaningful information regarding picture point intensities intermediate to the received picture element or pixel intensities. Only a few of these proposed systems do provide means in the receiver for developing a meaningfully interpolated pictorial output.
In U.S. Pat. No. 2,921,124 alternate sample and alternate field embodiments are disclosed for reducing channel capacity by discarding preselected signal periods (samples or fields) of a continuous succession of signal periods prior to transmission. At the receiving station the received signal data, consisting of only the retained signal periods, is restored to a signal equivalent to the original continuous succession of signal periods by using a one-dimensional interpolation technique on the received signal data. A similar one-dimensional interpolation technique is used on received data in U.S. Pat. No. 3,051,778 to restore the equivalent of scan lines alterntely deleted in the transmitter.
In U.S. Pat. No. 3,366,739 every fifth frame of a video image is transmitted and the intermediate four frames between consecutively transmitted frames are linearly interpolated in the receiver by combining progressively different complementary percentages of the consecutively transmitted frames. The system uses three variable output circuits which perform a multiplying function to accomplish this linear interpolation.
U.S. Pat. No. 3,725,684 teaches an implementation of an electronic calculating machine which performs a triple linear interpolation on data to develop a desired output quantity dependent on two input independent variables. The calculating machine forms sums and differences in a digital manner and products and quotients in an analog manner.
U.S. Pat. No. 3,996,456 discloses, in a one-dimensional recursive interpolation embodiment, the combination of a plurality of sample and hold circuits forming an analog shift register and of a computation unit to form a one-dimensional recursive interpolator. This patent further discloses a two-dimensional recursive interpolation embodiment wherein a single one-dimensional recursive interpolator scans, at a relatively rapid rate, the interpolated outputs of a series of slower one-dimensional interpolators to obtain a graphical output of a two-dimensional transducer array which includes interpolative information in the direction of both axes of the array.
In U.S. Pat. No. 4,032,977 expanded gray scale information is recovered from quantized video input data in a raster scanned imaging system by utilizing an interpolation process to predict a gray scale value for each element of output data from the quantized levels of an M by N matrix of input data elements. The prediction matrix for each output data element includes the spatially corresponding input data elements, together with vertically and horizontally adjacent input data elements.
None of the above-described prior art systems teaches or suggests applicant's simple apparatus (or method) for image reconstitution which is responsive to a sequence of received data-compacted pixels representing a two-dimensional coarse block image of a remote scene for computing by double linear interpolations intermediate picture point intensities in each of a plurality of horizontal lines to smoothly shade in the received coarse block image.